POSITIVES: The Pro Circuit complete Engine Performance Package turns the average CRF450R or RX model into a fire-breathing dragon that fears nothing! The performance gains throughout the power curve are impressive, and the configuration we tested had a Pro exhaust system that is slightly longer with smaller outlet diameters for sound requirements. We think this helped smooth the power out, making it less aggressive down low compared to their non-sound-restricted exhaust system. The clutch has a slightly harder pull, but we found with the performance increases we didn’t use the clutch as much, and it was more about throttle control. We definitely preferred that. Although straight race gas is preferred by Pro Circuit, it is not a necessity and can be mixed half and half. That is always a relief on the pocket book.

NEGATIVES: We tested a kick-start model, and unless we got it to top dead center and kicked all the way through, it was tough to start. With an electric start, this might go away. The price tag for the complete package we tested can be tough to swallow for the average consumer.

BOTTOM LINE: This is not a performance package that everyone will crave, but for the riders needing or wanting all the power possible out of a CRF450R or RX machine, the performance gains with this complete package are impressive throughout the entire power curve. It just has more everywhere. The cost is substantial in the configuration we tested, but this package is designed for a professional-level rider, and going fast is almost always expensive.